1. Field of the Invention
The present invention is directed to materials for filling dental root canals.
2. Description of Related Art
Dental root canal treatment generally involves three stages: shaping, cleaning and obturation (generally involving filling and sealing). The purpose of performing dental root canal treatment is to remove infected dental pulp tissue inside the pulp chamber and root canals, and to fill/seal the vacant space with a biocompatible material. More specifically, the ultimate objective of root canal treatment is to eliminate the infection inside the dental root system and to tightly seal or obturate, in three dimensions (3-D), the tiny openings at the end of the root canal, (referred in the profession as an apex). Failure to completely seal the apex or the root canal in 3-D leads to micro-leakage, which will lead to future bacteria colonization inside the root canal system, and re-infection and possible loss of the tooth. Micro-leakage is the most common cause of tooth failure.
Heretofore, root canal treatment processes involve placement of a root canal filling or sealing point or cone in a prepared root canal to plug the root canal, ideally in a manner to eliminate micro-leakage. In the past twenty-plus years, leading dentists and scientists have improved and revolutionized the shaping and cleaning part of the root canal treatment process. But the basic filling technique still lags behind due to antiquated manufacturing process dated more than 50 years ago. The existing filling points and the process of application thereof do not lend themselves well to providing a good seal of the root canal apex.
The most commonly used root canal filling material for many years is a biocompatible latex compound commonly called Gutta Percha, which comprises trans-polyisoprene, with a chemical composition of 1,4-trans-polyisoprene (TPI). Gutta Percha can be softened by heat to increase its plasticity comparing to other rubber based material. It is chemically inert therefore it is more biocompatible. Gutta Percha also hold its dimension quite well when change from heated liquid alpha phase to cooled solid beta stage.
The way to use Gutta Percha to fill/seal the root canal is to make it into a tapered cone shape “cone” or “point”, commonly called Gutta Percha point or cone (hereinafter throughout the present disclosure, “point” and “cone” are used interchangeably to refer to the root canal filling material). Heretofore, root canal filling points are formed of a filling material that is shaped into slender cones each having a small taper angle (e.g., 5-10 degrees). Each point is made into a particular taper shape that matches the shaping instrument (file) used by dentists to shape a root canal cavity for subsequent filling. The traditional way of making these points is by manual labor, specifically hand rolling Gutta Percha material into points to match shaping files. The Gutta Percha material needs to be softened first with higher temperature. Then being rolled into the point while being cooled to hold the final shape. This method of making the points has been in existence for over 50 years without much change. It is grossly inaccurate and risks material contamination since it is mostly handled by human hands.
There are a few automated and/or semi-automatic systems designed to make Gutta Percha points. They share same basic design approach, which mimic human hands rolling motion. These machines either use two rollers or one roller against one moving belt to roll points. There are several short comings with these machines. They are rather unstable and not efficient enough. They need constant adjustments for accuracy. Further, they are limited to rolling cones using only Gutta Percha based materials but not materials that have a different consistency compared to Gutta Percha materials.
U.S. Pat. No. 5,089,183 discloses a method of manufacturing appliances for use in filling endodontically prepared root canals with filler material, which involves inserting a shaft of a carrier into an uncured Gutta Percha material provided in a cavity of a block, heating and allowing the material to adhere to the carrier shaft. This process is low throughput, as it adds further complication to the making of a filler point for root canal.
It can be seen that the current root canal treatment procedures involve complex and challenging steps, which use cones that may be improperly shaped, which result in poor obturation leading to micro-leakage.
It would be desirable to develop an improved root canal filling cone that lend itself to mass production, and a manufacturing process for high throughput production of root canal filling cones.